(1). Field of the Invention
The invention relates to a method of reducing nitride residue in the fabrication of integrated circuits, and more particularly, to a method of reducing nitride residue by changing the nitride film surface to a hydrophilic state in the manufacture of integrated circuits.
(2). Description of the Prior Art
In the manufacture of integrated circuit devices, particles and residues on a nitride layer can have serious consequences for the quality of VLSI circuit manufacturing. The residues and particles occurring during nitride deposition and photolithographic developing play a major role in degrading the yield of wafers. It has been observed during after development inspection (ADI) and after etching inspection (AEI) that many tiny particles, discoloration, pattern lifting, and extra patterns have occurred. Pattern lifting will cause loss of field oxide, resulting in decreased wafer yield.
Co-pending U.S. patent application Ser. No. 09/040,434 to C. W. Cho et al filed on Mar. 18, 1998 discloses that cleaning a wafer with NH.sub.4 OH--H.sub.2 O.sub.2 (APM), HCl--H.sub.2 O.sub.2 (HPM), and H.sub.2 SO.sub.4 --H.sub.2 O.sub.2 (SPM) will leave the surface of the wafer in a hydrophillic state due to the oxidizing nature of peroxide (H.sub.2 O.sub.2). This is a problem if the surface is a polysilicon film. The invention of Cho et al cleans impurities and residue from a hydrophillic surface.
In the book, Integrated Circuit Fabrication Technology, by David J. Elliot, McGraw-Hill Book Company, NY, N.Y., c. 1982, pp. 111-112, the author discusses pre-photoresist cleaning of wafers using a sulfuric acid-hydrogen peroxide solution. U.S. Pat. No. 5,607,543 to Eisenberg et al teaches a hydrofluoric acid (HF) cleaning of a polysilicon layer before deposition of a silicon nitride layer, then HF cleaning of the silicon nitride layer to remove silicon dioxide or oxynitride after field oxidation. U.S. Pat. No. 5,413,670 to Langan et al discloses etching or cleaning of silicon nitride using NF.sub.3. U.S. Pat. No. 5,294,570 to Fleming, Jr. et al teaches cleaning a wafer with a strong acid and a small amount of a fluorine-containing compound such as HF. U.S. Pat. No. 5,181,985 to Lampert et al shows a water spray and HF gas can be used to clean a wafer and O.sub.2 and HCl gas can be used to make the surface hydrophillic.